474 PROFESSOR GREGORY ON 



banks of the Firth of Clyde, the level of which must always have regulated that 

 of Loch Fine since the present form of the coast has existed. 



There was, however, a circumstance which at first tended to throw some 

 doubt on this conclusion, according to which the marine forms of the Glenshira 

 sand must have come from Loch Fine. For although the known and described ma- 

 rine Diatoms found in the sand occur on our coasts, yet I was struck with the fact 

 that out of upwards of fifty new or undescribed forms, there seemed to be no 

 trace in deposits from the Firth of Clyde, examined by more than one naturalist 

 during the progress of my investigation. The fact of these forms being unde- 

 scribed was prima facie evidence that they had not yet occurred on the British 

 coasts. 



Yet it was evident that the formation of the Glenshira sand was, geologically 

 speaking, very recent ; so recent, indeed, that we could not suppose any number 

 of species to have since become extinct. I came, accordingly, to the conclusion, 

 that these undescribed forms must still exist in the waters of Loch Fine, or, what 

 is the same thing, of the Firth of Clyde. I was therefore desirous to examine 

 with care deposits from these waters, and this, during the past six months, I 

 have been enabled fully to do. 



The materials which I have examined are the following : — 



1. A small quantity of dirt or sand washed from some nests of Lima hians, 

 dredged in Lamlash Bay on the 19 th of July last, in 4 fathoms, by Professor 

 Allman. This material, though, when cleaned, very scanty, proved the richest 

 of all. 



2. Four dredgings, made by myself, with the kind assistance of the Duke of 

 Argyll, in Loch Fine, at different points within two or three miles of Inveraray. 

 These were all different, and three of them were interesting. They were taken at 

 depths of from 14 to 18 fathoms, early in October last. 



3. Three dredgings made at the same time by the Rev. Dr Barclay, in Loch 

 Fine, off Strachur, at depths of 15, 20, and GO fathoms, also in October last. 



4. Three materials forwarded to me in October by the Rev. Mr Miles of Glas- 

 gow, who was for some time on the Holy Island, in Lamlash Bay. 



One of these was washed from the nests of Lima'Jiians, as I had reported the 

 richness of the former. These last were from 7 fathoms in Lamlash Bay, This 

 material, dredged, I think, in June, was not so rich in Diatoms as Professor All- 

 man's, but yet contained many interesting forms. 



The second was a coarse red sand, dredged off Invercloy, Arran, which was 

 rather poor. 



The third was a mass of Corallina officinalis, taken with the hand, in rocky 

 pools, at Corregills, Arran, when the tide was low. The Corallina proved to have 

 been a good Diatom trap, and yielded a material, not remarkable for the number 



